The present invention refers to an acetabular socket supporting ring comprising a supporting ring having at least one attaching strap for a cement-free attachment in and on the corresponding bone portions, a socket cup comprising a part for receiving the joint ball, the socket cup being pivotably adjustable in the supporting ring and capable of being attached to the supporting ring by a securing element without the use of bone cement. Such an acetabular socket is known from the European Patent Application No. 0 123 514. Whilst therein the idea of adjusting the socket cup is disclosed, the securing element is relatively complicated and limited.
Acetabular socket supporting rings are known in further different embodiments and are mainly used in problematic hip joint revision operations. In particular, such problems result from the bone-resorbing action of the bone cement, mostly causing large-volume bone defects. In this case, the anchorage of a standardized cement-free acetabular implant is generally extremely difficult. In the case of dysplastic hips, as well, an anchorage of the hip joint socket is very problematic.
The supporting implants of this prior art are secured in the acetabulum by bone screws, and the hip joint socket is cemented in by bone cement. However, such an arrangement again involves the known drawbacks of the use of bone cement, more particularly a bone-resorbing action and an insufficient long-term vibration resistance, whereby the implant is loosened. Besides the need of using bone cement for the anchorage of the socket, the previously known socket supporting rings have the further disadvantage of being insertable in the pelvis in the exactly correct position only to a limited extent.
Based on the above mentioned prior art, it is the object of the present invention to provide an acetabular socket supporting ring which allows a cement-free implantation, on one hand, and a more precise, secure and simpler alignment of the socket in the pelvis and thus also with respect to the shaft, on the other hand.
This object is attained by an acetabular socket supporting ring, comprising a supporting ring having at least one attaching strap for a cement-free attachment in and on the corresponding bone portions, a socket cup comprising a part for receiving the joint ball, the socket cup being pivotably adjustable in the supporting ring and capable of being attached to the supporting ring by a securing element without the use of bone cement, wherein the supporting ring is internally provided with a cylindrical portion having an internal thread for receiving the securing element which has a self-locking external thread, and with a following spherical portion for receiving the socket cup, and wherein the part for receiving the joint ball is an insert, generally of plastics material.
In the first place, no bone cement is used for the anchorage of the socket supporting ring, and furthermore, the modular design allows a very precise adjustment of the socket cup.